Environmental Engineering Reference
In-Depth Information
confused with resuspension). Since vehicle emissions depend on the engine opera-
tion (i.e. driving situation), exhaust emissions are calculated as a function of average
speed and for three driving conditions: urban, rural and highway.
Uncertainties and Calculation Procedure
The COPERT methodology can be used to calculate a traffic emission inventory
both with a top-down approach and with a bottom-up approach. For countries for
which the required input data are not available at low level, it seems to be more
appropriate to start at NUTS level 0 (national level) and to allocate emissions to
other NUTS levels with the help of available surrogate data.
For countries where the required input is available at smaller NUTS level
(including for example traffic counting) it has been proposed to make use of this
information and to apply a bottom-up approach, building the national total by sum-
ming up emissions from the smaller units. An example of this procedure is pre-
sented by
[3]
in calculating emission for the road transport sector in Sardinia
(Italy). Emissions in Sardinia were calculated as the sum of contributions from each
municipality; the specific elements of each municipality necessary for the estimates
were previously analyzed and evaluated. Application of the methodology at higher
spatial resolution has to be done only when more detailed data are available from
the user. Several input data in applying the methodology can obviously be only
estimates and there is a certain degree of uncertainty in estimating these data.
The variables necessary to carry out the calculations are listed in Table
1
, together
with their qualitative uncertainty. Some of the so-called “soft” variables are associ-
ated with large uncertainty. The assignment of an initial value from scratch to each
soft variable is difficult, however some of them are suggested by COPERT IV for
each country, and others can be found in national transportation studies. Other
required variables are known with less uncertainty.
Using these variables and the fuel consumption factors of each COPERT IV
vehicle category, in terms of grams of fuel per kilometer, the annual fuel consump-
tion for gasoline, diesel and LPG is estimated. The software estimates the fuel
consumption and its percentage difference from the actual consumption; if this
difference isn't acceptable some soft variables should be modified. When a reliable
result is obtained, all the “soft” variables used for this accepted estimate are used
as an input to calculate the emissions using the COPERT IV emission factors.
The Emission Inventory
The collection of the necessary input data to calculate the emissions in the urban
area of Naples has required the contribution of agencies and institutions. ISTAT
(the Italian Institute of Statistics), the Ministry of Transport and Navigation
[4]
,
